Bosch Exxcel Classic 1400 – pungent, rubbery ‘warm’ smell ?

Our machine is around 8 years old, last week I replaced the brushes in the motor after the drum stopped turning.

Did a handful of washes fine, then at the weekend we came in from the garden to a very pungent, rubbery (I wouldnt say burning) smell coming from the washer, it was nearing the end of the cycle so I stood watching it until it finished.
Last night I checked the motor again, found one of the brushes did not move freely in its holder at all – so a bit of filing sorted that – I also cleaned the commutator with some fine abrasive. Put a half load on afterwards, ran it with the back off, but could not detect any smell coming from or around the motor, caught a very feint whiff now and again around the machine.

Fast forward to tonight, machine back in situ – normal load, really strong smell again 🙁 , feeling the door glass, I did wonder if it felt a little too wam for a 40 degree wash, but then I cant say I have felt the door regularly before.

Any ideas?,. if it was the motor, would it not smell really bad when on its spin cycle?

I did wonder whether to try a cold wash to eliminate an issue with the heating element/stat ?

Sorry for the long post,. appreciate any help 😀